The correct option is A P → 1, 3. Q → 2, 4. R → 5. S → 1, 3.
Limiting friction between A and B is fl=12 N &
Limiting friction between B & surface is fl=12 N
For B to move, net force on it should overcome friction from surface, i.e., resultant of FB & friction by A on B should be more than 12 N
For A to move net force on it i.e., FA+f or FA−f or f−FA should be greater than zero here f is friction between B & A which need not be 12 N.